Pathological Factor
Viral particles have been visualized by EM in intestinal epithelial cells and in epithelial cells located in the lower part of the villi, suggesting that the intestine is the site of replication. Astrovirus pathogenesis has been studied in lambs and calves, using ovine and bovine astrovirus isolates, respectively. Infection of lambs induces a mild transient diarrhea that occurs 2 days after infection and lasts approximately 2 days. Infection of calves with at least one strain of bovine astrovirus did not induce diarrheal illness, although the infection was associated with sloughing of infected villus cells.